The present invention relates to a combustion equipment for use in domestic heating, etc.
Conventionally, for the combustion equipment of the type referred to above, a lift vaporizing type combustion equipment used in an oil stove or the like is already known, which is generally shown in FIG. 1. Referring to FIG. 1, a wick 1 is vertically movably positioned between an inner guide sleeve 2 and an outer guide sleeve 3. The respective upper end portions of the inner guide sleeve 2 and the outer guide sleeve 3 form an inner fire plate 4 and an outer fire plate 5 onto which an inner flame cylinder 6 and an outer flame cylinder 7 are respectively mounted. The tip end of the wick 1 is, when the combustion takes place, exposed in the interior of a combustion portion 8 defined between the inner and outer flame cylinders 6 and 7, whereat the fuel is vaporized. The inner flame cylinder 6, the outer flame cylinder 7 and an outer cylinder 9 are disposed in generally concentric relation with each other sequentially in this order from inside of the device and are integrally coupled by a setting pin 10. Both the inner flame cylinder 6 and the outer flame cylinder 7 have many air holes 11. An inner top plate 12 which closes an opening portion at the upper end of the inner flame cylinder 6 is formed with a top hole 13 leading into an upper portion of the inner flame cylinder from the inside of the inner flame cylinder 6. There is placed a flame deflecting plate 14 on the inner top plate 12. The outer cylinder 9 has a neck portion 15 formed at the upper end thereof. Further, there is formed a red heat portion 16 in the outer flame cylinder 7 above the neck portion 15, which portion 16 has through holes 17 each with a large mouth. The combustion equipment further includes a heat permeable cylinder 18 which is made of heat permeable material such as glass or the like and put on the outer cylinder 9. An outer top plate 19 is placed at the upper end of the red heat portion 16 in such a manner as to close the upper end of an outer air path 20 formed between the red heat portion 16 and the heat permeable cylinder 18, thereby settling the heat permeable cylinder 18. In the above-described construction, when the wick 1 is lighted to start burning, the combustion gas at high temperatures rises up in the combustion portion 8, resulting in a draft. Accordingly, the air necessary for combustion is supplied, from the air holes 11 of the inner and outer flame cylinder 6 and 7 and the through holes 17 of the red heat portion 16, into the combustion portion 8. Thus, the combustion is continued, red-heating the red heat portion 16, thereby to obtain the radiant heat.
In the prior art arrangement, however, such drawbacks as described below cannot be avoided.
As shown in FIG. 1, in a normal intense combustion, a secondary flame f1 is formed over the inner and the outer flame cylinders 6 and 7, thereby to burn completely the non-burnt components coming up through the combustion portion 8. Accordingly, the exhaust gas displays favorable characteristics. On the contrary, however, in the case where only a litte of the wick 1 is exposed and the combustion volume is small, the flame comes down into the combustion portion 8 as indicated by f2. In this case, the flame f3 formed in the air holes 11 and the through holes 17 comes not to be formed above the flame f2. In such a state as above, the characteristics of the exhaust gas, particularly, CO/CO.sub.2 characteristic has been rapidly deteriorated. Moreover, in the case where the combustion device is used for a long period of time in a room which is tightly closed up, the combustion volume is gradually decreased in accordance with the decrease in density of oxygen. Therefore, if the flame falls down inside the combustion portion 8 as described above, a large quantity of carbon monoxide is generated. It was found out from the measurement of the exhaust gas in the prior art combustion equipment that the above-described phenomena result from the flow of the combustion gas and the air.
FIG. 2 shows the distribution of CO measured in the heightwise direction taken along the line A--A' (namely, in the outer air path 20 between the outer cylinder 9 or the heat permeable cylinder 18, and the outer flame cylinder 7) and the line B--B' (that is, in the inside of the inner flame cylinder 6) both at the time of strong combustion and at the time of weak combustion. At the position A--A' when the combustion is strong, the density of Co is immediately increased just above the neck portion 15 of the outer cylinder 9, and becomes the highest value at the upper middle portion thereof, and is decreased again near at the upper end portion of the outer air path 20. Nevertheless, the density of CO has a value over 500 ppm at the upper end portion of the outer air path 20. However, during the strong combustion, since the flame f1 almost completely burns the gas, the characteristic of the exhaust gas is satisfactory. During weak combustion, the contribution of the density of CO is similar to that during the strong combustion. The density of CO is about 250 ppm near the upper end of the outer air path 20 when it is burnt weakly. In this case, however, the flame f2 falls down, and accordingly CO is discharged directly into the atmosphere from the through holes 17 near the upper end of the red heat portion 18. At the position taken along the line B--B', either during strong combustion or weak combustion, the distribution of the density of CO displays a similar curve. Even when the combustion is weak, the density of CO is considerably high, namely over 1000 ppm near the upper end of the inner flame cylinder 6, which CO is directly discharged into the atmosphere.
Thus, from the above facts, the flow of the air and the combustion gas in the combustion equipment is as follows. Namely, as shown in FIG. 1, there is a main flow indicated by black arrows, and a flow indicated by broken line arrows. In other words, there is a flow (a) of the exhaust gas which is not completely burnt and running from the combustion portion 8 to the outer air path 20, and a flow (b) of the exhaust gas which is not completely burnt and leaking out from the combustion portion 8 into the interior of the inner flame cylinder 6. Therefore, if the flame falls into the combustion portion 8 as indicated by f2 when the combustion is weak, with no flame being formed thereabove, the combustion gas including CO of high density is discharged directly from the air holes 11 and the top hole 13 in the upper part of the inner flame cyliner 6, or from the through holes 17 above the red heat portion 16 into the atmosphere. Thus, such rapid deterioration of CO/CO.sub.2 characteristic during weak combustion as described earlier is clearly due to the fact that the combustion gas including highly concentrated CO which has leaked into the inside of the inner flame cylinder 6 and the outer air path 20 is discharged directly into the atmosphere.
As described hereinabove, in order to prevent the deterioration of the exhaust gas characteristic in the case where the volume of combustion is reduced so as to be small, it has been conventionally carried out that the amount of air supplied from the lower parts of the inner and the outer flame cylinders 6 and 7 into the combustion portion 8 has been relatively restricted. In this case, however, it has been disadvantageous because the ignition characteristic is worsened or a yellow fire is produced in the combustion portion 8 because of the reduction in the amount of air supplied into the combustion portion 8. Furthermore, since the air for combustion is also reduced in the case where the density of oxygen in the room is reduced (the oxygen deficient state), there have been dangerous possibilities that much CO is generated. Moreover, in the prior art arrangement, if the flame finally falls down into the combustion portion, the exhaust gas characteristic is deteriorated, and therefore the prior art arrangement is not a good arrangement.